Re: formula for great circle computation

Organization: Delta Internet Services, Anaheim, CA
Date:         13 Oct 95 01:30:22 
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In <airliners.1995.1581@ohare.Chicago.COM>, (C. Michael Barnett ) writes:

>I wonder if anyone can provide me with the formulae to calculate great
>circle course and distance given the latitude and longitude of the
>departure point and destination.  I'm writing a corporate flight
>scheduling program in Microsoft Access (ie visual basic), and need to
>figure leg distances and directions.

I had the same question a few years ago when I was working for an outfit
called SystemOne (at the time, the data processing and information
services arm of Texas Air).  I talked to one of the programmers on on
our "Phoenix" flight planning system and was surprised to find that the
Phoenix system used an algorithm that took into account the fact that
the Earth is oblate rather than spherical.  I never followed-up with
this information, but I wonder how much difference is involved between
the two algorithms.

For a short route, say LAX - SFO, I doubt there's a significant
difference.  But from LAX to Sydney?  At that distance, could the
difference between a spherical great-circle route and an oblate route be
measured in kilometers?

--           Eric Chevalier       Compu$erve: 76010,2463         ---------------------          Prodigy: GCXJ11A